A. Technical Field
The present invention relates to: a production process of a hydrophilic crosslinked polymer, more particularly, a production process in which hydrophilic crosslinked polymers such as water-absorbent resins can be dried uniformly with good efficiency.
B. Background Art
Generally, a hydrophilic crosslinked polymer is produced by polymerizing a solution including a hydrophilic monomer and a crosslinking agent, and then drying the resultant polymer. As a drying method, various methods such as static drying, stirring drying, and pneumatic drying are known, and these methods are properly employed according to natures and usages of polymers.
In the case where the hydrophilic crosslinked polymer is, for example, a water-absorbent resin, it is difficult to apply the stirring drying and the pneumatic drying, and the drying needs to be carried out in a static state, because the obtained polymer is usually a hydrogel and has strong tackiness and aggregates in the midway of drying.
However, though a surface portion is fast dried by the drying in a static state, there is a problem that an internal potion with which a hot wind is difficult to touch is hardly dried and the drying becomes non-uniform. Also, when the water content is dried to about 1.about.8 weight % by the static drying, there is a problem that partly excessively dried portions occur and these portions are deteriorated and have much soluble content. For the purpose of solving this problem, it is carried out to grind dried products in the midway of drying and then further dry them (Japanese Patent Publication (Kohyo) 08-506363 and so on), but it is still insufficient.